Drawing synthetic thermoplastic yarn

ABSTRACT

Filamentary yarn composed of thermoplastic synthetic, organic polymers is uniformly drawn at high speed by directing a stream of heated liquid into the path of the yarn to heat the latter to drawing temperature at less than drawing tension and immediately thereafter drawing the yarn by passing it over one or more snubbing pins arranged close to but out of contact with the liquid stream.

United States Patent Bergwerk DRAWING SYNTHETIC THERMOPLASTIC YARN [72]lnventor: Walter Bergwerk, Harrogate, England [73] Assignee: ImperialChemical Industries Limited, London, England [22] Filed: Oct. 5, 1970[211 App]. No.: 77,791

Related US. Application Data [62] Division of Ser. No. 768,960, Oct. 7,,1968, Pat.

52 US. Cl ..2s/s9.s, 264/210, l8/D1G. 17 51 1111.01. ..D02j 1/22 [58]Field of Search .....l8/l FS, 1 FT, 1 F2, DlG.l7, 18/ DIG. 53; 264/210R, 210 F, 288, 290

[56] References Cited UNITED STATES PATENTS I 3,091,805 6/1963 Dusenburg..18/l FT X 1151 3,681,826 1 51 Aug. 8, 1972 2/1967 Pitzl ..264/2l0 F UX2,289,232 7/1942 Babcock ..l8/ 1 FT UX 3,009,231

11/1961 Kleekomm et at]. .18/1 FF UX Primary Examiner-Robert L. Spicer,Jr.

Attorney-Thomas J. Morgan, Stephen D. Murphyand Robert J. Blanke *[57]ABSTRACT Filamentary yarn synthetic, organic polymers is uniformly drawnat high speed by directing a stream of heated liquid into the path ofthe yarn to heat the latter to drawing temperature at less than drawingtension and immediately thereafter drawing the yarn by passing it overone or more snubbing pins arranged close to but out of contact with theliquid stream.

4 Claim, 2 Drawing Figures composed of thermoplastic DRAWING SYNTHETICTHERMOPLASTIC YARN RELATED U.S. APPLICATION This invention, whichrelates to apparatus for uniformly drawing filamentary yarns composed ofthermoplastic, synthetic, organic polymers and to a process for drawingsuch yarns, is a divisional application of copending application Ser.No. 768,960, now US. Pat. No. 3,557,273 filed Oct. 7, 1968.

Apparatus and processes for orienting synthetic thermoplastic yarnswhich have been proposed are many and varied, some being specificallydesigned for use with yarns of particular polymers and others being ofmore general utility. Apparatus heretofore described has includeddrawing by means of heated snubbing pins, heated feed rolls, partly orcompletely liquid-immersed snubbing pins and liquid or vapor baths. Manyof these forms of apparatus possess limitations, as for example limiteddrawing speed or not entirely uniform products. I

We have now found that uniform drawing at high speeds may be effected bymeans of a combination of a stream of hot liquid and one or moresnubbing pins.

According to the present invention we provide apparatus for drawingfilamentary yarns composed of thermoplastic synthetic organic polymerscomprising means for supplying yarn to a drawing device, means forwithdrawing yarn from the drawing device at a higher rate than thesupply rate and means for collecting the drawn yarn, wherein the drawingdevice comprises a supply of temperature-controlled liquid and means fordirecting a stream of the liquid into the path of the incoming yarn justprior to passing the yarn over snubbing means, whereby the yarn israised to the desired drawing temperature, said snubbing means being outof direct contact with the liquid stream and so arranged as to cause inoperation a sudden change in direction of the yarn whereby liquidentrained in the yarn is thrown off.

Further according to the present invention we also provide a process forthe high speed uniform drawing of filamentary yarns composed ofthermoplastic synthetic organic polymers, wherein yarn is heated to adesired drawing temperature by a stream of liquid directed into the pathof the yarn just prior to passage of the yarn over snubbing meansarranged close to but not in direct contact with said stream.

Any liquid which does not attack the yarn to be drawn may be used toheat the yarn prior to drawing on the snubbing means and water isgenerally the useful liquid. The liquid may be supplied from a reservoirof liquid held at the required temperature to which the liquid afterpassing through the drawing device is recirculated.

Alternatively the liquid may be continuously circulated through thedrawing device at the desired temperature being either run to wasteafter passage therethrough or recirculated with addition of heat tomaintain the temperature substantially constant. Lubricating or othersubstances may be applied to the yarn simply by dissolving or dispersingsuch materials in the heating liquid.

The means for directing the liquid onto the yarn may be, for example, ajet or flume by means of which the direction of the issuing liquid canbe controlled. The direction of the issuing liquid may be counterorcocurrent in relation to the direction of the yarn travel.

Snubbing means may conveniently have the form of one or more metal orceramic pins, preferably of cylindrical shape, though other shapes maybe used, arranged close to, but out of direct contact with the stream ofheating liquid. In this way substantially no loss of heat from the yarnoccurs before it reaches the snubbing means whereon the tension in theyarn is raised until drawing ensues. The snubbing pin or pins is or arearranged so as to cause in operation the sudden change or changes ofdirection of travel of the yarn to throw off adhering liquid but thearrangement is such that the temperature of the yarn is not allowed tofall very far below the desired drawing temperature until drawing issubstantially complete.

The main function of the snubbing means in this invention is to raisethe tension in the yarn, which already has been brought to the desireddrawing temperature by means of the liquid jet, to that at which drawingensues. The snubbing means may be heated but it is not necessary to doso for adjustment of the temperature of the liquid jet and its positionrelative to the snubbing means will ensure that the yarn passes over thelatter at the desired drawing temperature.

The function of the liquid jet is to raise the yarn to the desireddrawing temperature, which temperature is chosen to suit the particularsynthetic polymer yarn to be drawn. The tension in the yarn passingthrough the liquid jet is kept lower than that at which drawingcommences under the applied temperature conditions. Thus operatingconditions are arranged such that substantially no drawing occurs untilthe yarn reaches the snubbing means. Control of the operating conditionsin this way results in the production of highly uniformly drawn yarn andsuch control is facilitated by the drawing device of the presentinvention, wherein heating of the yarn takes place substantially in theabsence of any tension raising influence.

It is only necessary to limit the length of the yarn immersed in theliquid jet so that the yarn tension is not raised to the drawing tensionat the temperature used by the liquid drag on the yarn travelling athigh speed.

Uniformity of the drawn yarn may be assessed in various ways and forpolyethylene terephthalate yarn we have used dyefleck or stripinesstests for this purpose. In the dyefleck test a uniform layer of drawnyarn is would onto a parallel tube by means of a lathe.

The bobbin and yarn are immersed in a cold acetone solution of thesolvent dyestuff Waxoline Red OS (Color Index No. 26105), a dyestuffwhich does not dye drawn yarn but dyes undrawn yarn red. After rinsingin acetone the tube is examined and the dyeflecks, that is lengths ofundrawn fiber, are counted. The result is expressed as the number ofdyeflecks per 24,000 feet of filament.

For assessing the stripiness of drawn yarn an eightend sateen fabric iswoven and dyed with an appropriate dyestuff for the particular syntheticpolymer yarn being assessed, as for example Lispersol fast scarlet B(Color lndex No. 11110) for polyethylene terephthalate using 2 percentof the dyestuff based on the weight of the fabric. The dyed fabric isexamined visually under natural and ultra-violet light for stripiness,i.e., uneven dyeing of lengths of warp or weft which are evident in thefabric as warp or weft stripes.

The liquid directing means and the snubbing means are convenientlyarranged in one unit.

A preferred embodiment of the apparatus of the invention comprising sucha unit is-illustrated by way of example, in the accompanying drawingwherein:

FIG. 1 diagrammatically shows in cross section a side elevation of adrawing device, together with representations of yarn supplying,withdrawing and collecting means.

FIG. 2 diagrammatically shows a sectional plan view of a drawing device.

In the apparatus of FIGS. 1 and 2, liquid at the required temperature issupplied from a source (not shown) through an inlet 1, to directingmeans, 2, which has the form of a truncated flume, 4, mounted within acontainer, 3. The liquid flows from the narrower end of the flume acrossthe path of entering yarn, 5, just before the yarn is passed over thefirst of a series of three snubbing pins 6, whereon the tension israised and drawing occurs. The snubbing pins are mounted on a carrier,7, which is attached to a cover, 8, of the container, 3, the whole beingdemountable to facilitate stringing-up of the yarn. The used liquid iscarried away by way of an outlet, 9, to waste or to a temperaturecontrolled reservoir (not shown).

Spun yamis supplied to the drawing device from a package, 10, by afeed/roll idler roll combination, ll, optionally by way of a tensioncontrol device, 12. Drawn yarn leaves the drawing device by a drawroll/idler r011 combination, l3, and is collected on a package, 14. v I

In an apparatus according to the invention the amount of entrainedliquid, if any, in the drawn yarn leaving the drawing device isdependent upon the number of snubbing pins of guides within the deviceand the sharpness of changes of direction incurred at each. It is notnecessary or indeed possible in the practice of the invention to ensurethat all entrained liquid is removed from the drawn yarn in the drawingdevice. It is often convenient to remove a substantial proportion ofentrained liquid in the drawing device and then to remove the remainderby, for example, heating the draw roll causing evaporation of the liquidthereon. Heating the draw roll serves a secondary function, that of heattreating the drawn yarn at controlled tension to modify the physicalproperties, in particular shrinkage, of the yarn.

By means of this invention uniformly drawn yarns may be obtained at highspeeds. Heating of the yarn to be drawn by liquid means, as in theinvention, enables higher speeds of drawing to be attained because ofthe improved uniformity and rate of heating-up of the yarn and becauseof the substantial absence of any snubbing surfaces in contact with theyarn at this stage. Likewise accurate temperature control is facilitatedby use of a large body of liquid in a temperaturecontrolled reservoir.Surprisingly we have found that filamentary yarns composed ofpolyethylene terephthalate, which are usually drawn at elevatedtemperatures between about 70 and 100C i.e., a temperature at or abovethe second order transition temperatures may be uniformly drawn by meansof a device according to this invention at temperatures approaching roomtemperature i.e., a temperature well below the second order transitiontemperature, without any apparent deterioration in uniformity. Ifinstead such polyethylene terephthalate yarns are drawn by means of anunheated snubbing surface alone, very uneven yarn is produced and onlyvery low speeds of drawing are possible without breakdown of the yarn.

By means of the present invention we have drawn polyethyleneterephthalate yarns at speeds up to 7,200 feet per minute, which was thelimit of the available winding units, .without the appearance ofnon-uniformities as assessed by the dyefleck test. By comparison using aknown drawing process wherein yarn is drawn between a heated feed roll(90C) and a cold drawn roll with a heated plate l40-l60C) intermediatethese rolls it was not possible to exceed a draw speed of about 5,000feet per minute without incurring the appearance of dyeflecks in theyarn.

Yarn composed of polyethylene terephthalate, 24 filaments of 5 denierper filament, drawn with a draw ratio of 3.22:1 in the apparatus ofFIGS. 1 and 2, using water at C as the heating liquid and a draw speedof 3,000 ft./min. gave a 40 denier drawn yarn which was highly uniformin respect of denier differences along its length.

A particular advantage of the high drawing speed attainable by thedevice of this invention is that the draw ing step may be combined withthe melt-spinning process in one stage and not as the usual two-stageprocess on separate apparatus, wherein drawing follows melt-spinning asa separate process, necessitated by the lower (than the melt-spinningwinding speed) drawing speed required with many other forms of drawingapparatus.

Any filamentary yarn which is composed of a thermoplastic,cold-drawable, synthetic polymer may be drawn by means of the device ofthis invention. For example we have drawn polyethylene terephthalate,nylon 66 and polypropylene yarns by means of the device.

The following examples illustratethe invention and the manner in whichit may be performed.

EXAMPLES 1-3 Filarnentary yarn composed of 24 filaments of polyethyleneterephthalate having total denier of 160 and a mean birefringence of 8.3X 10' is drawn at a draw-ratio of 3.22:1 using an apparatus similar tothat of FIG. 1 and 2 but having only a single ceramic pin of 3/16 inchdiameter as the snubbing means. The heating liquid is water, containing1 percent by weight of a lubricant/antistat dispersed therein,maintained at C directed co-current on to the yarn and giving animmersed yarn length of 2 inches. The angle of contact of the yarn withthe snubbing pin is 90. Yarn drawn at different speeds using a cool(30C., Example 1) or heated (C, Examples 2-3) draw roll shows nodyeflecks and has the following properties:

Fabric woven from the yarn produced in Examples 2 and 3 shows nostripiness.

It is noteworthy that when the Example 2 is repeated using 4% inchesyarn immersed length and a draw speed of 3,500 feet per minute unevendrawing, with the production of dyeflecks, resulted dueto some drawingtaking place in the liquid stream by reason of the increased water drag.

EXAMPLE 4 In this Example the polyester yarn as used in Exam- 7 ple 1-3is very satisfactorily drawn in the same apparatus at a draw rate of3.22:1 to produce dyefleckfree yarn using a reduced liquid temperatureof 56C, a draw speed of 2,000 feet per minute and a cold (C) draw roll.The drawn yarn has the following properties:

Tenacity, g/den. 4.1

Extension at break, 28.l

Boiling water shrinkage, 32. 1

EXAMPLE 5 EXAMPLE 6 Nylon 66 yarn of 803 denier and 34 filaments (meanbirefringence 5.2 X 10') is drawn in the apparatus of the precedingexamples at 5,000 ft./min. using a draw ratio of 3.27:1 and a cold drawroll. The yarn draws satisfactorily in the presence of a stream of water(temperature 76C) to produce uniform yarn of similar properties. In theabsence of the water stream the yarn shows marked non-uniformity ofdrawing when knitted into a fabric and dyed with Durazol Blue 2R (ColorIndex No. 34140).

6 EXAMPLE 7 The apparatus of FIGS. 1 and 2 is used with an arrangementof five ceramic pins of 3/16 inch diameter to draw the same polyesteryarn used in Example 4 at a draw speed of 2,000 ft./min. and a drawratio of 3.22: 1. A liquid temperature of 82C is used with a hot drawroll at 140C. The five pins are arranged one above the other one-halfinch apart in staggered fashion (A inch stagger between adjacent pinsand the yarn takes a zigzag path over the pins with contact angles onthe first and fifth pins of 130 and 45 respectively, and on the threeintermediate pins of C.

The yam produced has substantially the same properties as yarn producedin Example 4 and is free from dyefiecks.

Having thus disclosed the invention, what is claimed 1. Apparatus fordrawing filamentary yarns composed of thermoplastic synthetic organicpolymers comprising a drawing device, means for supplying yarn to thedrawing device, means for withdrawing yarn from the drawing device at ahigher rate than the ture-controlled liquid, snubbing means and meansfor heating the yarn substantially in the absence of any tension-raisinginfluence to a desired drawing temperature, said last-named meansincluding flume means for directing a stream of the liquid into the pathof the incoming yarn just prior to passing the yarn over said snubbingmeans, whereby the yarn is raised to the desired drawing temperature,said snubbing means being out of direct contact with the liquid streamand so arranged as to cause in operation a sudden change in direction ofthe yarn whereby liquid entrained in the yarn is thrown off.

2. Apparatus according to claim 1 wherein the snubbing means includes atleast one cylindrical pin.

3. Apparatus according to claim 1 wherein the yarn supplying andwithdrawing means are rollers.

4. Apparatus according to claim 3 including means for heating thewithdrawing rollers.

2. Apparatus according to claim 1 wherein the snubbing means includes atleast one cylindrical pin.
 3. Apparatus according to claim 1 wherein theyarn supplying and withdrawing means are rollers.
 4. Apparatus accordingto claim 3 including means for heating the withdrawing rollers.